1. Field of the Invention
The present invention relates to a printer for forming an image on a recording medium in such a manner that an electrostatic latent image is formed on a surface of an image carrier, a toner image is formed on the surface of the image carrier by means of causing the electrostatic latent image to absorb toner, and transfer and fixing of the toner image are applied to the recording medium, and an image forming method of forming the image.
2. Description of the Related Art
Hitherto, a development of a film photographed by a camera and a print of photography are implemented in a so-called photofinishing laboratory, which is facility different-from a general store such as a photo studio. However, recently, there become popular photo studios having a small type of apparatus (hereinafter it is referred to as a mini-laboratory) for carrying out processing from printing to development necessary for printing of photography, so that a development of a film and a print of photography are performed in the photo studio. As the mini-laboratory to be installed in the photo studio, generally there is known an apparatus for obtaining a photographic image in such a manner that an image is exposed on a photographic paper in accordance with image data read from films and the like, and the photographic paper is passed through liquid such as developer and fixer. However, according to such a mini-laboratory, there is a need of replenishment of developer, fixer and water, and a periodical cleaning of a tank for saving those liquids, and in addition there is a need of processing for liquid waste, which will take trouble and cost for processing.
On the other hand, a so-called electrophotographic system of printer, which needs no processing for developer, fixer, water and liquid waste, is widely used in copying machines. According to the electrophotographic system of printer, an image is formed on a recording medium in such a manner that an electrostatic latent image is formed on a surface of an image carrier, the electrostatic latent image adsorbs a toner so that a toner image is formed on the surface of the image carrier, and transfer and fixing of the toner image to the recording medium are applied. However, an image, which is obtained through the electrophotographic system of printer, is worse than the conventional mini-laboratory in connection with an image quality such as a gloss on an image surface and thus it is not competent as a photographic image. Accordingly, it is considered that an electrophotographic system of printer is not competent to be applied to the mini-laboratory.
However, recently, a technology related to the image quality of the electrophotographic system of printer is advanced and thus it is considered that the electrophotographic system of printer is applied to the mini-laboratory. For example, there is proposed a printer (cf. Japanese Patent Laid Open Gazette TokuKai. 2003-5545 (pages 2–4, FIG. 1)) having a primary fixer for applying a primary fixing in which a toner image transferred to a recording medium is fixed on the recording medium, and a secondary fixer for applying a secondary fixing in which a surface of the fixed toner image is smoothed to provide a gloss, the secondary fixer being disposed downstream with respect to the primary fixer in the conveyance path for the recording medium. While the printer disclosed in Japanese Patent Laid Open Gazette TokuKai. 2003-5545 is an apparatus that is supposed in application to copying machines and the like, the image quality of the image obtained through the printer is not worse than that of the photographic image obtained through the conventional mini-laboratory, and thus it is considered that that printer has a performance capable of being applied to the mini-laboratory.
According to the printer disclosed in Japanese Patent Laid Open Gazette TokuKai. 2003-5545, the secondary fixer for obtaining an image not worse than the photographic image applies the secondary fixing as set forth below.
First, the toner image, which is fixed on the recording medium by the primary fixer, is heated to fuse the toner, and a surface of the toner image fused in toner is urged to a smooth glossy surface. And the toner image is cooled in the urged state to solidify the fused toner. Thereafter, the toner image is separated from the glossy surface. This processing makes it possible to obtain an image of high picture quality having a gloss not worse than the photographic image.
The above-mentioned secondary fixing needs an extremely long processing time as compared with the primary fixing, since it takes a lot of time for a cooling of the toner image. For this reason, for example, in the event that a toner image is fixed on a plurality of recording media sequentially conveyed on a conveyance path in the apparatus, it would happen that before the secondary fixing for the preceding recording medium is terminated, the primary fixing for the subsequent recording medium is terminated. At that time, regardless of execution of the secondary fixing still, if the recording medium subjected to the primary fixing is conveyed to the secondary fixer, two recording media would collide with one another in the secondary fixer. In order to avoid such a trouble, according to the printer disclosed in Japanese Patent Laid Open Gazette TokuKai. 2003-5545, there is adopted such a sequence that the primary fixing is executed at a time interval of an extent that two recording media do not collide with one another in the secondary fixer, and in timing after the secondary fixing for the preceding recording medium is terminated and the preceding recording medium is conveyed from the secondary fixer to the further downstream side, the subsequent recording medium is conveyed to the secondary fixer.
As a typical example of this type of sequence, there is raised such a sequence that after the secondary fixing for the preceding recording medium is terminated and the recording medium is conveyed from the secondary fixer to a further downstream side, the primary fixing for the subsequent recording medium is initiated.
FIG. 4 is a view showing a typical example of a sequence consisting of the primary fixing and the secondary fixing for a plurality of recording media that are sequentially conveyed on a conveyance path, which is prevented from a collision on the conveyance path of two recording media continuously conveyed.
According to the sequence shown in FIG. 4, for example, the primary fixing for the recording medium for the second sheet is initiated after the secondary fixing for the recording medium for the first sheet is terminated. Also with respect to the recording medium for the third sheet et seqq., the fixing processing is applied in accordance with the same sequence. According to such a sequence, it is possible to prevent a collision on the conveyance path for two recording mediums to be continuously conveyed. However, according to the sequence shown in FIG. 4, the primary fixer would idle, after the primary fixing for the recording medium as an object in processing is terminated, in a state that no recording medium as an object in processing exists, until the secondary fixing for the preceding recording medium is terminated and the recording medium is conveyed from the secondary fixer to a further downstream side. Also with respect to the secondary fixer, the secondary would idle, after the secondary fixing for the recording medium as an object in processing is terminated, in a state that no recording medium as an object in processing exists, until the primary fixing for the subsequent recording medium is terminated and the recording medium is conveyed from the primary fixed to the secondary fixer. According to the sequence shown in FIG. 4, the idling operation of the primary fixer and the secondary fixer is repeated, and thus the working efficiency of the printer will be lowered.
In order to enhance the efficiency of the fixing processing of the primary fixing and the secondary fixing, there is considered, for example, a sequence that after the primary fixing for the recording medium as an object in processing is terminated, even if the secondary fixing for the preceding recording medium is not yet terminated, the primary fixing for the subsequent recording medium is initiated in timing that there is established a time interval in such an extent that no collision with the preceding recording medium occurs on the conveyance path. However, even such a sequence is concerned, there exists a period of time of the idling operation of the primary fixer and the secondary fixer, although it is reduced as compared with the sequence shown in FIG. 4, and thus the working efficiency of the printer will be lowered by the corresponding.